changegroup: track changelog to manifest revision map explicitly

Previously, self._nextclrevtolocalrev was only populated as part
of the changelog lookup callback. But cgpacker._close() was looking
at self._nextclrevtolocalrev on every invocation.

Since self._nextclrevtolocalrev is for communicating the mapping
of changelog revisions to manifest revisions, this commit refactors
the code to make that explicit.

The changelog state now stores this mapping. And after the changelog
group is emitted, we update self._clrevtolocalrev with that dict.
self._nextclrevtolocalrev is unused and has been deleted.

Differential Revision: https://phab.mercurial-scm.org/D4190

mercurial/changegroup.py

@@ -661,14 +661,10 b' class cgpacker(object):'
         # Maps CL revs to per-revlog revisions. Cleared in close() at
         # the end of each group.
         self._clrevtolocalrev = {}
-        self._nextclrevtolocalrev = {}
 
     def _close(self):
         # Ellipses serving mode.
         self._clrevtolocalrev.clear()
-        if self._nextclrevtolocalrev is not None:
-            self._clrevtolocalrev = self._nextclrevtolocalrev
-            self._nextclrevtolocalrev = None
 
         return closechunk()
 
@@ -784,6 +780,9 b' class cgpacker(object):'
         mfs = clstate['mfs']
         changedfiles = clstate['changedfiles']
 
+        if self._ellipses:
+            self._clrevtolocalrev = clstate['clrevtomanifestrev']
+
         # We need to make sure that the linkrev in the changegroup refers to
         # the first changeset that introduced the manifest or file revision.
         # The fastpath is usually safer than the slowpath, because the filelogs
@@ -853,6 +852,7 b' class cgpacker(object):'
         # TODO violates storage abstraction.
         mfrevlog = mfl._revlog
         changedfiles = set()
+        clrevtomanifestrev = {}
 
         # Callback for the changelog, used to collect changed files and
         # manifest nodes.
@@ -876,8 +876,7 b' class cgpacker(object):'
                     # manifest revnum to look up for this cl revnum. (Part of
                     # mapping changelog ellipsis parents to manifest ellipsis
                     # parents)
-                    self._nextclrevtolocalrev.setdefault(cl.rev(x),
-                                                         mfrevlog.rev(n))
+                    clrevtomanifestrev.setdefault(cl.rev(x), mfrevlog.rev(n))
                 # We can't trust the changed files list in the changeset if the
                 # client requested a shallow clone.
                 if self._isshallow:
@@ -903,6 +902,7 b' class cgpacker(object):'
             'clrevorder': clrevorder,
             'mfs': mfs,
             'changedfiles': changedfiles,
+            'clrevtomanifestrev': clrevtomanifestrev,
         }
 
         gen = self.group(revs, cl, True, lookupcl, units=_('changesets'))